Anatomy, Head and Neck, Zygomatic

The zygomatic bone works with the masticatory muscles to control the mastication process and aesthetic function of the face.[12] The zygomatic bones function as the origins for the masticatory muscles, especially the masseter muscles, where they help them attach inferiorly.[13] Their frontal processes are associated with the temporalis muscle in that their fibers run parallel from them and insert onto the mandibular coronoid process.[13]

As mentioned previously, usually, the zygomatic bone is a single bone bounded by sutures, but it can be divided by extra sutures into two or more parts.[2] For the most part, there is an extra suture that runs perpendicularly from the facial portion of the maxillozygomatic suture and dorsolaterally to the zygomatic bone, which imparts it a bipartite morphology.[2] The zygomaticofacial foramen, located at the mid-lateral surface of the zygomatic bone that gives off the zygomaticofacial nerve and zygomaticofacial vessels, has also been found to vary from being double or being absent.[14] According to a study that examined 102 dry hemicrania, the zygomaticoforamen ranged from being absent to have as many as four small openings, and half of the specimens had one foramen.[14]

The zygomatic bone could also vary among different ethnic populations. According to Oettle et al., prominence of the zygomatic bone was associated with Eastern Asian populations and populations from Eastern Europe.[15] However, there was diffusion of this trait in populations across the Behring Sea and the Arctic, North America, and South America areas. Some Arctic groups show a prominence of the zygomatic bone to adapt to extreme cold conditions while groups from Australia, Malaysia, and Oceania show some prominence of the zygomatic bone.[15]

Because the zygomatic bone may fracture during facial trauma and may involve other facial structures, such as the frontal bone, maxilla bone, temporal bone, and orbit, it is critical first to obtain a thorough, prompt ophthalmologic exam.[16] Zygomaticomaxillary complex fractures can significantly alter the structure and aesthetic beauty of the midface, including the globe, and often involve blindness or serious eye injuries. These injuries have significant associations with ocular injuries and visual sequelae than most other types of midfacial injuries. Also, researchers discovered that patients who fractured the zygomatic bone after facial trauma were seven times as likely to sustain an eye injury than those who did not experience a bony fracture after facial trauma.[16]

For the surgical management of patients with zygomatic bone fractures, several examinations are necessary. First is the assessment of gross vision as well as the presence of traumatic optic neuropathy.[16] During these tests, the presence of afferent pupillary defects or red color desaturation requires evaluation, as they may appear in patients with zygomatic bone fractures and red color perception is first to disappear in optic nerve compromise.[16] Testing of extraocular movement and visual fields is also necessary, as a constraint in extraocular muscle movement could indicate muscle entrapment. A forced duction test with an anesthetic or computed tomography scans can be performed to assess extraocular muscle entrapment.[16] Finally, sensation in the V2 distribution should undergo evaluation, as sensation in this region almost always decreases in patients with malar fractures.[16]

As mentioned previously, the zygomatic bone forms the prominence of the cheeks, a portion of the lateral wall, the orbit floor, and some parts of the temporal fossa and infratemporal fossa. The zygomatic bone is essential for enduring the forces of mastication and transmitting forces from the maxilla.[2] It also plays a vital role in maintaining the aesthetic beauty and function of the face and protecting the eyes. The zygomatic arch also gives rise to the masseter muscle, which is the major jaw adductor in mammals.[3] The zygomatic bone also connects the facial skeleton to the cranial bones by joining the maxilla to the temporal and frontal bones, which forms a portion of the lateral border of the bony orbit.[3]

The zygomatic bone may also fracture during facial trauma. Fractures of the zygomatic bone are among the most common types of facial fracture and primarily result from assaults and motor vehicle accidents.[16] These fractures are typically complex, as the zygomatic bone articulates with four other bones, and these fractures rarely occur in isolation. The masseter muscles are also the major muscle providing the most significant deforming force on the zygomatic bones.[16] Additionally, because the zygomatic bone forms a substantial portion of the orbital wall and floor, zygomatic bone fractures often involve displacement of the orbit. Therefore, a thorough ophthalmologic exam should be conducted for patients with zygomaticomaxillary complex fractures to assess the severity of facial trauma.[16]

Although rare, fibrous dysplasia of the zygomatic bone may occur. The disease often manifests as a continuously growing mass in late childhood.[17] Even though it frequently involves the maxilla and the mandible, some rare cases may include the zygomatic bone. Fibrous dysplasia of the zygomatic may result in many symptoms, such as orbital dysplasia, diplopia, and proptosis.[17]